Conventionally, in the HSDPA service, a technique such as an adaptive modulation/demodulation and correction scheme (AMCS: hereinafter, “AMC scheme”) based on adaptive wireless link control (link adaptation) such as channel encoding proposed in Non-Patent Document 1, etc., is applied.
The AMC scheme is a scheme according to which wireless transmission parameters such as the number of data modulation multiple values, a correction scheme, an encoding rate of the correction, the number of data modulation multiple values, the code spreading rate (SF: Spreading Factor) of the time and frequency axes, the number of multiple code multiplex are switched corresponding to the state of the transmission path of each user to efficiently execute the high-speed packet data transmission.
For example, as to the data modulation, as the state of the transmission path becomes better, the maximum throughput of the communication system can be increased by switching the modulation of the system from a QPSK (Quadrature Phase Shift Keying) modulation to a more efficient multiple-value modulation such as an 8 PSK modulation, a 16 QAM (Quadrature Amplitude Modulation) modulation. Herein, various wireless transmission parameter sets used for the AMC scheme are referred to as “MCS (Modulation and Coding Scheme) mode”. An example of the MCS mode is shown in FIG. 12.
As shown in FIG. 13, in an HSDPA (see Non-Patent Document 2), a downlink pilot channel 3, a downlink common control channel 4, a downlink shared control channel 5, a downlink shared data channel 6, an uplink control channel 7, an uplink data channel 8, etc., are present.
One downlink pilot channel 3 is present in each cell 9 and includes a common pilot channel (CPICH: Common Pilot Channel) and a dedicated pilot channel (DPICH: Dedicated Pilot Channel).
One downlink common control channel 4 is present in each cell and includes a reporting information, paging information (a paging indicator channel, a paging channel), synchronization information (a synchronization channel), etc., of a base station apparatus 1.
One downlink shared control channel 5 is present in each cell and includes and time-division-multiplexes (TDM: Time Division Multiplex) individual control information, etc., to each mobile station apparatus 2 (each user).
One downlink shared data channel 6 is present in each cell and time-division-multiplexes individual transmission data, etc., to each mobile station apparatus.
The uplink control channel 7 includes an uplink dedicated control channel, and control information, measurement and reporting information, etc., from the mobile station apparatus are transmitted thereon.
The uplink data channel 8 includes an uplink dedicated data channel, and transmission data from the mobile station apparatus is transmitted thereon.
Referring to FIG. 14, description will be given for a flow of signals between the base station apparatus and the mobile station apparatus in the HSDPA. As shown in FIG. 14, when a wireless link is established between the mobile station apparatus and the base station apparatus, the mobile station apparatus always receives an HS-SCCH (High Speed Shared Control CHannel) that is one of downlink shared control channels, detects information on a mobile station apparatus ID (UE ID: User Equipment IDentifier) contained in an MCS field of sub-frame control information of the downlink shared control channel HS-SCCH, and judges whether the ID coincides with the mobile station apparatus ID of the own mobile station.
When the mobile station apparatus has detected the mobile station apparatus ID of the mobile station on the downlink shared control channel HS-SCCH: the mobile station apparatus receives a sub-frame of an HS-DSCH (High Speed Downlink Shared CHannel) contained in a downlink shared data channel HS-PDSCH (High Speed Physical Downlink Shared Channel) that is one of downlink shared data channels, that has been transmitted being delayed by a predetermined time delay (Delay 1) from the head of a sub-frame of the downlink shared control channel HS-SCCH, using MCS mode information contained in an MCS information field of the sub-frame control information transmitted on the downlink shared control channel HS-SCCH; and executes data demodulation according to the designated MCS mode information.
When user data to be transmitted occurs, the mobile station apparatus transmits the data through a DPCH (Dedicated Physical CHannel) that is an uplink dedicated data channel.
The mobile station apparatus measures the reception quality of the common pilot channel CPICH contained in the downlink common control channel of the base station apparatus, that represents the state of a downlink transmission path (downlink wireless transmission path property estimation or channel estimation). Downlink signal quality information CQI (Channel Quality Indication) judged from the result of the downlink wireless transmission path property estimation is provided as feedback to the base station apparatus through an HS-DSCH (High Speed Downlink Shared CHannel) sub-frame of an uplink dedicated control channel HS-DPCCH (High Speed Dedicated Physical Control Channel).
The base station apparatus selects an appropriate MCS mode according to this downlink signal quality information CQI and transmits the data in the AMC scheme.
Because the HSDPA employs hybrid automatic re-transmission (HARQ: Hybrid Automatic Repeat reQuest), the mobile station apparatus transmits ACK/NACK (Acknowledgement/Negative Acknowledgements) that is the received notice acknowledgement information through an HARQ information field of an HS-DSCH sub-frame of the HS-DPCCH.
The above mobile station apparatus in an HSDPA needs to receive control information (downlink shared control channel) that indicates whether the data is addressed to the own station even when the mobile station apparatus is standing by for data during the packet communication. Therefore, electric power is always consumed by a receiving portion because the receiving portion can not execute intermittent reception (DRX) operation even when data reception time is short.
Because the AMC scheme is employed, the mobile station apparatus needs to always provide the downlink signal quality information CQI as feedback to the base station apparatus. Therefore, the electric power is always consumed by the transmitting portion. Especially, a high-speed data transmitting scheme such as the HSDPA is often used for services for which data downloading is repeated intermittently such as WEB viewing. Therefore, the power consumption of the mobile station apparatus becomes much even when the time for transmitting/receiving data is short.
To solve this problem, as shown in Patent Document 1, a method has been proposed according to which a base station apparatus has a means of notifying a mobile station apparatus of transmission/reception state updating information that indicates update of the state of whether the mobile station apparatus can receive data, and the mobile station apparatus controls the data transmission/reception state based on the transmission/reception state updating information.
As shown in Patent Document 2, a controlling method has been proposed according to which a base station apparatus includes a means of setting a downlink shared control channel with a mobile station apparatus and transmitting a data transmission notice to the mobile station apparatus, and the mobile station apparatus includes a means of responding to the data transmission notice during setting of an uplink control channel and starting transmission of downlink signal quality information CQI at predetermined intervals to the base station apparatus.
As shown in Patent Document 3, a method has been proposed according to which a mobile station apparatus or a base station apparatus judges a monitoring method based on the data amount and the mobile station apparatus controls the data transmission/reception state by notifying the counterpart of the monitoring information.
On the other hand, in the HSDPA, the downlink common control channel includes the paging indicator Channel PICH (Paging Indicator CHannel), a downlink primary common control PCCPCH (Primary Common Control Physical CHannel), and a downlink secondary common control channel SCCPCH (Secondary Common Control Physical CHannel).
The paging indicator channel PICH is a channel that is set with a purpose of reducing the intermittent reception rate to improve the battery saving of the mobile station apparatus. The paging indicator channel PICH transmits a short paging indicator PI (Paging Indicator) to notify the mobile station apparatus of the presence or the absence of arrival of transmission. The mobile station apparatus that is standing by receives only this paging indicator PI during the intermittent reception period thereof. Only when the paging indicator PI reports the presence of arrival of transmission, the mobile station apparatus receives a paging channel PCH (Paging CHannel) in a wireless frame on the downlink secondary common control channel SCCPCH, that corresponds to the paging indicator PI. Paging indicators PI are grouped into a plurality of groups that each are group of mobile station apparatuses, and the frequency of transmission arrival per one group can be reduced to a very low level. Therefore, the mobile station apparatus that is standing by has to receive only a short paging indicator PI and the frequency of receiving a long paging channel PCH can be reduced to a very low level (see Non-Patent Document 3).
In the HSDPA, when the power of the mobile station apparatus is turned on, before entering a soft handover mode or in an intermittent reception mode while standing by for communication, the mobile station apparatus needs to detect a cell with which path loss caused by long-section variation and shadowing variation obtained by averaging momentary fading variation is minimal (before entering the soft handover mode, a cell with which this path loss is second minimal). This is a process of detecting a cell that has a scramble code of a common pilot channel CPICH for which power for receiving is largest in the downlink. This process is referred to as “cell search” meaning to search a cell to be connected to a wireless link (see Non-Patent Document 3).
In a cell search in the intermittent reception mode (idle mode) during standing by, through a paging channel PCH in a wireless frame on the downlink secondary common control channel SCCPCH, the mobile station apparatus receives information on the types of scramble codes of the cell which is connected to a wireless ring or receives the paging channel PCH in the intermittent reception mode and surrounding cells to be searched (about 20 cells), and on the difference in scramble code timing of the common pilot channel CPICH between the cell being connected and the surrounding cells.
Therefore, for the mobile station apparatus, the types of the scramble codes of the surrounding cells to be searched and the average reception timing of the common pilot channel CPICH at the mobile station apparatus are known. Therefore, a search for the surrounding cells in a short time is enabled. In the intermittent reception mode during standing by, generally, reception of the paging indicator channel PICH and the cell search are simultaneously executed (see Non-Patent Document 3).    Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-147049    Patent Document 2: Japanese Laid-Open Patent Publication No. 2003-199173    Patent Document 3: Japanese Laid-Open Patent Publication No. 2004-289234    Non-Patent Document 1: T. Ue, S. Sampei, and N. Morinaga, “Symbol Rate and Modulation Level-Controlled Adaptive Modulation/TDMA/TDD system for High-Bit-Rate Wireless Data Transmission”, IEEE Transaction, VT, pp. 1134-1147, Vol. 47, no. 4, Nov. 1998    Non-Patent Document 2: Reference related to HSDPA specification of 3GPP TR (Technical Report) 25. 858 and 3GPP http://www.3gpp.org/ftp/Specs/html-info/25-series.htm    Non-Patent Document 3: Keiji Tachikawa, “W-CDMA Mobile Communication Systems”, ISBN4-621-04894-5, P114